Good explanation Samfox. The USAF needs to fix the TOLD situation among the various fleets of aircraft. It amazes me that at my employer, within 15 seconds, I can have the TOLD data sent to me via ACARs for any runway and any intersection I need to depart from. Instead, the USAF uses original chart data, effectively requiring the crews to build TOLD data from scratch. When SDPs came along, they were welcome with open arms from the aircrew. However, the USAF lowered the DER and obstacle clearance heights to 0' and now they may be going away??? This is just stupid and it isn't very safe.

For years I've seen the KC-10 TOLD slowly evolve and be re-engineered based on the new set of guys flying it. We just keep making it more complex for the sake of being safe. However, we've done just the opposite. We have had a few close calls now where the aircrew used the SDP data for a particular runway but failed to check the all engine requirements for the SID they were cleared to fly. The result, we've had crews takeoff and weren't able to meet the climb gradient required with all engines operating!!!

In my last years as an IP/EP on the KC-10 I learned that no matter where I was flying to, if Jepps supported the airfield, I always made a copy of their charts. There's much more information on Jepp charts than there are on the NACO's. At the very least, always take the Jepp 10-9 Airfield diagram pages with you.

Whenever we had to use Jepps, the USAF would only authorize us to fly the VOR approches ... and usually only to one runway. I guess the VOR approaches were the only ones in which they felt comfortable approving due to the lack of obstacle information. Operationally, this didn't always work out. Approach ATC doesn't always have the luxury to clear you some odd ball or opposite direction approach because that's the only one you're company has allowed you to fly. That is when those additional copies I made came in handy.

 

So to re-open this topic, has anyone come to a simple yet definitive difference between a SDP and the data that we use via flight manual/laptop computer (C-5/KC-10) or aircraft mission computer (C-17)?

I was under the impression that the C-17 (my aircraft) considered climbout data from the end of the runway and that the Jep SDP considered climbout data beginning from the CFL - but now I've concluded that the C-17 mission computer does consider the amount of runway following rotation (TORA/ERAC) into the obstacle clearance equation...

The SDP obviously allows us to go "lower" than our mission computer does, because in the C-17 when we can't get data against a OEI climb gradient, we are allowed to clear the requirement from our computer as long as we ensure that we meet the Jep SDP's COF (Climb Out Factor - flight path)and CFL.

But wherein is the difference between Jep SDP and Air Force climbouts? It would seem again that with the Jep SDP we are allowed to be "lower" than the AF Terps...anyone?

 

It's because the Jep SDP uses "runway cutback" in calcs (when you leave the ground vice passing departure end). If I understand your question correctly...

 

"Back in the Day" - Frankfurt - there used to be a procedure for calculating TOLD data from intersections in the dep planning checklist. That was when SDPs and Jepps info first made it's way on the scene. Then it disappeared. It was explained to me that they eliminated it because every time we did an intersection takeoff using the SDP we invalidated it because we rotated later on the runway than the SDPs calculated for a given wt and temp. Of course noise abatement at EDDF was brutal so an intersection takeoff would lower our alt passing the sensors.